1. Field of the Technology
The present invention relates to a color cathode ray tube apparatus of the type which includes an in-line electronic gun and a deflection yoke for producing a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field.
2. Description of the Prior Art
In general, a deflection yoke to be applied on a color cathode ray tube apparatus which includes an in-line type electron gun, is designed to produce a pincushion type horizontal deflection magnetic field shown in FIG. 1 and barrel type vertical deflection magnetic field shown in FIG. 2. Therefore, such conventional color cathode ray tube apparatus does not require any complex convergence circuit, and can be designated as a self-convergence system. However, such conventional apparatus has a problem in that the electron beam spots produced by projection on a phosphor screen become elliptic shapes as shown in FIG. 3, as designated by b, g and r respectively for blue, green and red beam spots corresponding to the electron beams from the electron gun beam outlets B, G and R, thereby lowering resolution.
It is considered that as shown in FIG. 4(a), the pincushion type horizontal deflection magnetic field can be decomposed into a uniform magnetic field 1a and a positive six pole magnetic field component 2a. Likewise, the barrel type vertical deflection magnetic field can be decomposed into a uniform magnetic field 1b and a negative six pole magnetic field component 2b. Therefore, it can be seen that the distortions of the beam spots b, g and r are produced by the positive and negative six pole magnetic field components 2a and 2b as shown in FIG. 5(a) and FIG. 5(b). As a result, the beam spot distortion produces discolorations similar to those caused by misconvergences between the central electron beam from the central electron gun and the side electron beams from the side electron guns, thereby leading to poor resolution.